The present invention relates to pulping apparatus for making a slurry out of a solid and liquid mixture for such things as paper making, and especially relates to pulp rotors that spin to mix solids and liquids into a slurry.
It is well known in the paper making industry to combine solid stock such as fibrous wood materials or recycled paper products with a liquid in a container generally known as a "pulper tub" having one or more pulp rotors. Such a rotor typically includes a plurality of vanes extending in a propeller-like fashion from a central axis of a rotor hub and the rotor spins to generate a circulatory motion in the mixture. Each vane includes a leading edge that serves, as the rotor spins, to mechanically shear fibrous components of the solid stock into smaller particles such as industrial paper making fibers. Hydraulic shear is also generated immediately above the rotor as it spins to further break up or defibrate the solid components. The rotor is typically placed adjacent a bed plate or an extraction plate in a well-known manner to assist in defibrating the solid materials.
In one form of such a pulping container or "pulper", the container is filled with one batch of solid and liquid materials, and then the rotor spins for a pre-determined period of time adjacent a bed plate having raised cutting edges to assist in defibrating the solid particles. The resulting slurry is then removed and processed into paper. In another well-known form of a "pulper", the liquid and solid materials are continuously fed into the container, and the rotor spins over an extraction plate defining extraction or feed-out holes that have circular cutting edges forming an entry to each feed hole that assist in breaking up the solid materials as the defibrated slurry continuously passes out of the feed-out holes to be further processed into paper.
Efforts to improve efficiencies of such rotors in "pulpers" have focused on decreasing power requirements to spin the rotor per unit of time to produce an acceptable slurry. For example, U.S. Pat. No. 3,889,885 issued on Jun. 17, 1975 to Couture and incorporated herein by reference discloses an improvement to pulper rotors wherein a plurality of fin-like "pumping vanes" are secured to and extend above upper surfaces of some vanes of a well known "Vokes" rotor to increase vortical circulation above the rotor. The increased circulation draws the liquid solid mixture more efficiently toward leading edges of the vanes, and in particular draws any solids suspended near or floating at a surface of the liquid down toward the rotor and corresponding bed or extraction plate. While such an improved vortical circulation decreases an overall rotating time period necessary to produce an acceptable slurry, the fin-like pumping vanes however also offer greater resistance to rotation of the vanes, and hence increase power requirements to rotate the vanes for the decreased rotating time period. Therefore the improvements shown in Couture and other known improved pulper rotors fail to decrease power requirements through any improvement in inherent mechanical defibrating capacities of the rotors.
Accordingly, it is the general object of the present invention to provide a channeled pulp rotor that overcomes deficiencies of the prior art.
It is a more specific object to provide a channeled pulp rotor that increases mechanical shear capacity of the rotor without significantly increasing power requirements to spin the rotor.
It is another specific object to provide a channeled pulp rotor that increases circulation of a slurry adjacent and above the rotor without significantly increasing power requirements to spin the rotor.
It is yet another object to provide a channeled pulp rotor that increases mechanical shear capacity of the rotor in a batch or continuous flow pulper.
These and other advantages and objects of the present invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.